ls swap engine mount fitment issues

[TA_C10]

Hey guys, 1970 c10 ls swap. Having fitment issues. I purchased the adapter plates from LMCTruck, and am currently using the stock rubber engine mounts and stock small block perches with the truck.

I went to test fit the engine yesterday and wasn't able to get the engine mount bolts to line up. I could get the driver side bolt in but when the passenger side laid down on the perch, the engine mount setup is too wide and doesn't allow the engine to sit all the way down in the perches so I couldn't get the engine down far enough to line up the hole for the bolt.

The perches are currently installed in the front mounting location on the cross member. Its where the previous 350 was installed.

What am I doing wrong, and how can I fix this issue? We tried everything we could think of to get the engine to squeeze into the perches but no go. It needs about 1" more to slide down into the perches. Seems so close but won't go in....

We had a thought to "slot" the perches bolt hole up a little on both sides to allow the holes to line up with the mounts but not sure if this is a good idea. The engine is going to sit up higher also because of this problem. Hopefully this won't cause any issues.

Only other option I can think of is to buy new ls swap perches and motor mounts to get around this issue.

If the original rubber mounts were thinner, it would allow it to slide down into the perches and fit. But I don't see anywhere I can get thinner motor mounts....

Thanks,
Tom